Post-Passivation Interconnect Adhesion via Under Bump Metallization

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Solution Overview

Problem

In semiconductor device fabrication, the interface between bumps and polymer layers in wafer level chip scale packaging (WLCSP) exhibits poor adhesion, leading to potential delamination due to moisture attack, which affects the reliability of interconnect structures.

Innovation Solution

A post-passivation interconnect (PPI) structure is formed by creating a bump structure with an under bump metallization (UBM) layer over a patterned interconnect layer, which is electrically connected to a conductive pad, and encapsulated with dielectric and protective layers to enhance adhesion and prevent delamination.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If post-passivation interconnect (PPI) lines are formed on passivation layers in WLCSP, then electrical connections can be established, but the interface between bumps and polymer layers exhibits poor adhesion leading to delamination due to moisture attack

Engineering Contradiction:

Improveadhesion between bumps and polymer layersVSAvoidmoisture attack causing delamination

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

An under bump metallurgy (UBM) layer is introduced as an intermediary between the bump and the polymer layer. This UBM layer serves as a mediator that improves adhesion at the bump-polymer interface and provides barrier properties against moisture attack, thereby preventing delamination while maintaining electrical connectivity.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The interconnect structure employs composite material design with multiple layers including the UBM layer, passivation layer, and polymer layer. Each layer contributes different properties: the UBM layer provides adhesion and moisture barrier, the passivation layer provides electrical insulation and protection, and the polymer layer provides structural support and encapsulation, together forming a composite structure that resolves the adhesion and moisture resistance issues.

Inventive Principle:

Principle #40Composite materials

2Ease of manufacture

If conventional interconnect structures are used without additional protective layers, then manufacturing is simpler, but adhesion between bumps and polymer layers is poor and delamination occurs

Engineering Contradiction:

Improvesimplicity of fabrication processVSAvoidadhesion and resistance to delamination

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The under bump metallurgy (UBM) layer is formed in advance before the final polymer encapsulation step. This preliminary action prepares the surface with improved adhesion properties and moisture barrier characteristics, ensuring that when the polymer layer is subsequently applied, strong bonding is achieved and delamination is prevented, without requiring complex post-processing steps.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS9859242B2Post-passivation interconnect structure and method of forming same

Publication Date: 2018.01.02 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

A semiconductor device including a dielectric layer formed on the surface of a post-passivation interconnect (PPI) structures. A polymer layer is formed on the dielectric layer and patterned with an opening to expose a portion of the dielectric layer. The exposed portion of the dielectric layer is then removed to expose a portion of the PPI structure. A solder bump is then formed over and electrically connected to the first portion of the PPI structure.